Removal of residual ethylene oxide from poly(ethylene oxide)

Abstract

Residual ethylene oxide is removed from poly(ethylene oxide) by the steps of adding to particles of high molecular weight poly(ethylene oxide) a finely divided solid particulate material which is capable of coating the poly(ethylene oxide) particles and impeding their agglomeration under conditions of heating, heating the particles of poly(ethylene oxide) at a temperature of at least 40° C. and preferably which is near their crystalline melting point, and maintaining the temperature for a sufficient time to reduce the ethylene oxide in the particles of poly(ethylene oxide) to ten ppm or less. In one embodiment, the poly(ethylene oxide) is heated by holding the particles in a heated enclosure; in another, it is heated as a slurry in a liquid medium; in yet another, it is heated by warm gas in a gaseously-fluidized bed; and in a fourth, it is heated by microwave radiation.

We claim: 
     
       1. A process for reducing the ethylene oxide content of high molecular weight polyethylene oxide, consisting essentially of: (1) adding to particles of poly(ethylene oxide) having a molecular weight of from about 100,000 to 7 million and which contain from about 20 to 70 ppm of ethylene oxide a finely divided solid particular material which is capable of coating said poly(ethylene oxide) particles and impeding their agglomeration under conditions of heating, said addition being conducted in a dry state; and   (2) removing ethylene oxide by agitating and and heating said particles of poly(ethylene oxide) in said dry state at a temperature of from about 40° C. to about 70° C. for a time sufficient to reduce the ethylene oxide level in said particles of poly(ethylene oxide) to ten ppm or less.   
     
     
       2. The process of claim 1 wherein said finely divided solid particular material is selected from the group consisting of silica, alumina, titania, talc, clay minerals, and ground limestone. 
     
     
       3. The process of claim 1 wherein said finely divided solid particulate material is selected from the group consisting of flour, graphite, pre-graphitic carbons, powdered sugar, and cotton linters. 
     
     
       4. The process of claim 1, wherein said particles of poly(ethylene oxide) are heated at a temperature of at least about 50° C. 
     
     
       5. The process of claim 1 wherein said particles of poly(ethylene oxide) are heated to a temperature in the range from about 58° C. to about 70° C. 
     
     
       6. The process of claim 1 wherein said heating step is accomplished by holding said particles of poly(ethylene oxide) in a heated enclosure. 
     
     
       7. The process of claim 1 wherein said heating step is accomplished by applying a stream of heated non-reacting gas to said particles of poly(ethylene oxide). 
     
     
       8. The process of claim 1 wherein said heating step is carried out by applying microwave radiation to said particles of poly(ethylene oxide). 
     
     
       9. The process of claim 1 wherein the level of residual ethylene oxide in the poly(ethylene oxide) is 2 ppm or less. 
     
     
       10. The process of claim 1 wherein the poly(ethylene oxide) has a molecular weight of from about 300,000 to 5 million. 
     
     
       11. A process for reducing the ethylene content of high molecular weight poly(ethylene oxide), consisting essentially of; adding to particles of poly(ethylene oxide) having a molecular weight of from about 100,000 to 7 million and which contain from about 20 to 70 ppm of ethylene oxide a finely divided silica which is capable of coating said poly(ethylene oxide) particles and impeding their agglomeration under conditions of heating, said addition being conducted in a dry state;   heating said particles of poly(ethylene oxide) in said dry state at a temperature of from about 40° C. to about 70° C. and agitating said particles during said heating; and   maintaining said temperature for a time sufficient to reduce the ethylene oxide level in said particles of poly(ethylene oxide) to ten ppm or less.